Symmetry-enforced topological nodal planes at the Fermi surface of a chiral magnet

• Published in: Nature (London) Vol. 594; no. 7863; pp. 374 - 379
• Main Authors: Wilde, Marc A., Dodenhöft, Matthias, Niedermayr, Arthur, Bauer, Andreas, Hirschmann, Moritz M., Alpin, Kirill, Schnyder, Andreas P., Pfleiderer, Christian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.06.2021; Nature Publishing Group
• Subjects: 639/766/119/2792/4128; 639/766/119/995; De Haas-Van Alphen effect; Density functional theory; Fermi surfaces; Ferromagnetism; Humanities and Social Sciences; Information technology; Magnetic fields; Magnets; Manganese; Manganese silicide; multidisciplinary; Quantum phenomena; Science; Science (multidisciplinary); Spectroscopy; Spectrum analysis; Spintronics; Stability; Symmetry; Topological spaces; Topology; Germany
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-021-03543-x

Despite recent efforts to advance spintronics devices and quantum information technology using materials with non-trivial topological properties, three key challenges are still unresolved 1 – 9 . First, the identification of topological band degeneracies that are generically rather than accidentally located at the Fermi level. Second, the ability to easily control such topological degeneracies. And third, the identification of generic topological degeneracies in large, multisheeted Fermi surfaces. By combining de Haas–van Alphen spectroscopy with density functional theory and band-topology calculations, here we show that the non-symmorphic symmetries 10 – 17 in chiral, ferromagnetic manganese silicide (MnSi) generate nodal planes (NPs) 11 , 12 , which enforce topological protectorates (TPs) with substantial Berry curvatures at the intersection of the NPs with the Fermi surface (FS) regardless of the complexity of the FS. We predict that these TPs will be accompanied by sizeable Fermi arcs subject to the direction of the magnetization. Deriving the symmetry conditions underlying topological NPs, we show that the 1,651 magnetic space groups comprise 7 grey groups and 26 black-and-white groups with topological NPs, including the space group of ferromagnetic MnSi. Thus, the identification of symmetry-enforced TPs, which can be controlled with a magnetic field, on the FS of MnSi suggests the existence of similar properties—amenable for technological exploitation—in a large number of materials. Measurements on a chiral magnet show that non-symmorphic symmetries enforce topological crossings exactly at the Fermi level in certain materials; these crossings can be controlled by an applied magnetic field.